1. Field of the Invention
The present invention relates to hand-held tools and, more particularly, to such tools as are useful for the application and shaping of moldable materials. More specifically, the present invention relates to a hand tool for finishing inside and outside rounded wall surfaces, contours, and columns with a cementitious material to provide a uniformly rounded surface configuration.
2. Description of the Prior Art
Plaster walls have been traditionally constructed by a labor-intensive process. A common wall requires the application of three individual plaster layers, each of which must be leveled and set prior to the application of the succeeding layer. Although considerable skill is required to achieve a flat, smooth surface over a large area, the end result is a wall having an unmistakable look and feel, along with superior sound insulation properties.
The use of such skilled labor runs counter to the present trends in the commercial and home construction industry. Emphasis today is on speed, efficiency, and cost-effectiveness towards the completion and profitability of construction projects. Competitive bidding pressures have made it increasingly difficult to rely on anything other than unskilled labor when bidding a construction project.
Except for the most expensive of custom installations, gypsum wall board, also know as "dry wall" has completely replaced plaster in the construction of walls and ceilings in modern homes and offices. Composed of a core of calcined gypsum, starch, water, and foam slurry sandwiched between special paper faces, gypsum board or dry wall retains the fire-resistant characteristics of gypsum plaster but can be installed with much less labor, and by less skilled workers. In addition, the use of dry wall brings very little "water" into a building, and thereby eliminates some of the waiting required with the curing and drying of gypsum plaster.
After the core material has hardened and bonded to the paper faces, the dry wall is cut to length, heated to drive off any residual moisture, and then bundled for shipping. For the majority of commercial and home construction applications the dry wall is cut into rectangular sheets of four (4) feet by eight-to-twelve (8-12) feet, and is one-half inch to five-eighths inch in thickness. Installation of the dry wall can occur over either steel or wood studs using self-tapping screws for metal studs and either screws or nails to fasten the dry wall to the wood support. After installation of the dry wall is complete, all of the joints between the boards and the indentations left by the nailing or screw attachments must be filled and smoothed before the surface of the dry wall is ready for final texturing or finishing.
The majority of dry wall panels used in finished wall constructions have a tapered edge to assist in forming a flush, invisible seam between adjacent panels when the joint finishing operation is completed. Finishing begins by the troweling of a layer of joint compound or plaster into the tapered edge joint formed along adjacent edges of adjoining dry wall panels. A paper or glass fiber reinforcing tape is then placed over the joint and covered with an additional layer of the joint compound. These first layers are allowed to dry and one or two finishing coats of the joint compound are then applied and sanded. A properly finished joint forms a wall that appears to be made of a solid sheet rather than discreet panels.
Flat gypsum board also can be used to form curved surfaces. When the curves are gentle, dry wall can conform to a large radius by simply bending the panels around a curving line of support studs. For somewhat sharper curves, the paper faces of the wall board can be moistened, which decreases the stiffness of the board prior to conforming it to the shapes required upon its installation. Drying causes the dry wall to again stiffen, permitting its attachment to the underlying support structure(s).
In custom and semi-custom residential construction, there has been a recent trend towards providing such visual features as rounded walls, recesses, columns, and bay window areas. In commercial buildings, the trend has been toward providing one or more "walls as art" located in the "common" areas. In each of these construction applications there are framing irregularities, creases, and/or gaps that are created when attaching the flat, dry wall materials to the supportive radius wall framing.
The majority of these features require radii that are very difficult to achieve by simply deforming the flat dry wall panels. Instead, the present practice is to cut the dry wall into multiple sections that are then pieced together to create a substantially curved surface. A smoothed, finished surface is then obtained by the application of either the joint compound or a plaster material to cover the joint irregularities. The multi-piece surface is thereby formed into a visually-continuous surface, having multiple-curved surfaces expressed therein.
However, achieving such a uniformly radiused finish has proven to be extraordinarily difficult for the dry wall laborers to achieve. In addition to requiring a higher level of skill on the part of the workman, it has proven necessary to devise specialized tools to assist the dry wall installers in obtaining the desired surface uniformity, such as the corner finishing tool of Kartler, U.S. Pat. No. 5,440,776. As noted in Perry, U.S. Pat. No. 4,669,970, workmen have frequently resorted to reshaping their trowels to approximate the working edges to the desired surface radius. Other workmen have attempted to maintain the required curvature by utilizing a bent piece of cardboard.
Neither of these solutions have proven to be particularly desirable. The modified trowel must be held at a specific angle relative to the dry wall surface throughout the finishing process. This includes maintaining the angle along the entire length of a specific, curved wall feature. Also, to maintain continuity from one curvature to another, this same angle must be carefully repeated. With respect to the use of cardboard, such improvised tools are not capable of uniformly maintaining an appropriate curvature or hand hold. Consequently, it has proven to be extraordinarily difficult to maintain a fixed angular position between the improvised tool and the work surface.
Ideally, it would be desirable to provide a plastering tool that is sufficiently adaptable as to be able to form curved surfaces at multiple locations, and not require specialized tools for each of various types of curved surfaces.